Regenerating teeth may be possible with injectable hydrogel, researchers find

16 Jun 2022 --- Researchers from the US-based New Jersey Institute of Technology (NJIT) have discovered an alternative to root canal treatments through tissue regeneration. The proposed alternate treatment is backed by a US$3 million grant from the National Institutes of Health.

The researchers created an injectable hydrogel to extract a person’s dental pulp stem cells directly to the disinfected cavity after a root canal.

The hydrogel, made up of biocompatible amino acid peptides that aggregate into fibers, provides biological cues for tissue growth and a scaffold structure to support it.

In the US, dentists conduct around 15 million root canals on infected teeth yearly, extracting the inflamed pulp and filling the emptied canal with inert materials like rubber and cement.

“One of the primary goals of this project is to determine the type of cells that reorganize and repopulate the regenerated tissue,” says Kumar, the principal investigator and bioengineer at NJIT.

Overcoming challenges
The research team explains that no FDA-approved technologies for successfully restoring native dental pulp are currently available. Through the study, researchers aim to create a materials-based therapy that does not contain living cells and may thus be purchased over-the-counter.

The researchers propose restoring damaged tissue in the tooth cavity by prompting the body to regenerate it.The researchers note that one of the core challenges tissue engineers face is creating blood vasculature, the plumbing that delivers nutrients to regenerated cells.

To address the problem, the team’s hydrogel contains a protein known as a vascular endothelial growth factor that stimulates the growth of new blood vessels, explains Emi Shimizu, co-investigator, Rutgers School of Dental Medicine at Rutgers University.

Restoring dental pulp
On children’s immature permanent teeth with necrotic pulp, a treatment called over-instrumentation stimulates new root growth by eliciting a healing response.

“Teeth lacking dental pulp are more vulnerable to cracking and can respond poorly to future bacterial infections and mechanical injuries,” adds Kumar. “We’d prefer to avoid killing and removing a child’s permanent tooth that is still growing but helps the roots thicken and lengthen.”

Regarding the children’s teeth, when the tissue outside the emptied canal is prodded, blood clots develop, which secrete a protein called growth factor that signals cells to make new tissue to support the root.

The researchers observed that some tissues regenerate but the process is disorganized as it lacks tissue differentiation and does not mimic soft tissue, Shimizu explains.

In contrast, the team’s hydrogel therapy mimics the body’s growth factor signaling. Additionally, when coupled with known antimicrobial mechanisms engineered into those materials, it can promote tissue healing and regeneration.

Preventing harmful bacterial growth
The research team also noted the importance of inhibiting the growth of harmful bacteria on the new tissue.

After a root canal, the researchers developed an injectable hydrogel that draws a person’s own dental pulp stem cells directly to the cleaned cavity.“Even in healthy oral microbial communities, the species that can cause disease, pathobionts, are usually at low levels. When they increase in numbers, a healthy microbiome can shift to a pathogenic one. Depending on the oral disease, different species increase,” says Carla Cugini, microbiologist and co-investigator at Rutgers School of Dental Medicine at Rutgers University.

Kumar’s antimicrobial peptide, which he designed for a different anti-infection purpose, was able to kill the bacteria P. aeruginosa by breaking its membrane.

“We will look at a panel of oral bacteria to determine if this antimicrobial peptide hydrogel, known as K6, is effective against them. It will not disrupt the entire microbiome because our localized delivery to the canal space and hydrogel properties ensure the peptide remains where we put it.”

A different hydrogel containing only the antibacterial peptide was tried in a second investigation. The findings revealed that it was capable of building scaffolds and effective when combined with peptides that promote blood vessel formation. The researchers intend to integrate and evaluate both therapies in a single hydrogel in the future.

In other developments, US-based University of Washington researchers developed the O-pH system, a cavity dental instrument that detects where tooth enamel is most vulnerable to plaque acidity.

By Nicole Kerr